1. Field of the Invention
The invention relates to an apparatus for interface measurement in a storage tank. In particular, the invention relates to an apparatus for continuously monitoring the water level at the bottom of a product storage tank.
2. Description of the Related Art
Many methods and techniques exist to detect an interface between product and water (herein referred to as a product-water interface), but due to the abrupt change in dielectric constant, capacitance techniques are most commonly employed. The drawback with using capacitance is that to provide adequate resolution, precise measurements are often necessary. This necessitates either careful circuit design or sophisticated signal processing which can be expensive and complex to implement.
Further, it is known to apply a co-axial transmission line to determine liquid-level in a tank. Electrical pulses are applied at the, line input. Changes in dielectric constant that result from the interface, cause the pulses to be reflected back to the line-input and from the measured reduction in pulse length, the liquid level is calculated. However, the measurement accuracy of this known system is limited by the need to make precision high speed measurements.